I recently tried the Unread app and was surprised to see a bunch of old items which have never shown up on Newsblur.com or the iOS app.
I haven’t found a proven case of an item which was hidden from a feed which I do see but I’ve found at least two feeds which simply do not ever show up using the official apps. https://getsatisfaction.com/newsblur/… makes it impossible to send the feed URLs but here are some search terms:
CICLOPS (the version with the lower follower count)
Science@NASA Headline News
I’m wondering if it’s possible that the Google Reader import had something like an invalid folder name since unlike the official apps, Unread simply displays all of the items without any structure.